The Effect of Photoperiod and Temperature on the Production of Gamic and Agamic Forms in Macrosiphum Euphorbiae (Thomas)

Apterous and alate Macrosiphum euphorbiae (Thomas) from a clone reproducing agamically since 1952 produced viviparae and sexuales when exposed to certain photoperiods and temperatures. The kinds of offspring produced were influenced by day length, parent type, "generation", and temperature. The greatest percentage alate viviparous females was produced when the day length was between 11 and 13 hours and when the first "generation" parents were apterous. The greatest percentage of apterous viviparous females was produced when the day length was greater than 13 hours and when the parents were First "generation" alatae. The greatest percentage of oviparous females was produced by second "generation" alatae and that of males by fourth "generation'' apterae. It is suggested that temperature does not influence directly the kind of offspring produced, hut does so indirectly by its effect on the number of light/dark cycles of an effective photoperiod that occur during the critical stage in the life of the aphid.